1. Field of the Invention
This invention generally relates to endotracheal tubes, and more particularly, to endotracheal tubes having a bendable portion designed to facilitate intubation of difficult airways (tracheal inlet opening) caused by anatomical variation, trauma and the like.
2. General Background and State of the Art
An endotracheal tube generally comprises a cylindrical tube used as an air passage to administer oxygen and anesthetic gases directly to the patient. The cylindrical tube terminates in an open distal end configured for insertion into the trachea and has an opposite open proximal end configured to be coupled to a gas source. The endotracheal tube typically has an inflatable cuff on the exterior of the cylindrical tube for forming a seal with the interior walls of the trachea. (See U.S. Pat. No. 3,460,541 to Doherty). The cuff functions to occlude the trachea which protects the trachea and lungs against aspiration of foreign substances. In particular, food, foreign bodies or digestive system contents are prevented from entering the lungs. The endotracheal tube is used primarily in surgery, but is also frequently used in emergency rooms and emergency in-the-field situations.
In surgical procedures requiring general anesthesia, the patient is rendered unconscious by administration of anesthetic agents including drugs and/or gases. The patient is also given a muscle relaxant/paralyzing agent to minimize the patient""s gagging response to the insertion of the endotracheal tube. A laryngoscope is placed in the mouth of the patient. The blade portion of the laryngoscope is used to push the tongue laterally and the intubating practitioner applies a lifting force to the laryngoscope handle in order to visualize the anatomical structures of the mouth and airway. A specific target area of the tracheal tube is the glottis, which is the opening between the vocal cords and the inlet to the trachea. The distal end of the endotracheal tube is inserted into the glottis and the inflatable cuff (balloon) is filled with air to create an airtight seal between the cuff walls and the interior walls of the trachea. This airtight seal allows for delivery of the oxygen and anesthetic gases with positive pressure directly to the air passages below the tip and the balloon.
Patient anatomies differ greatly and fall into specific categories that are grouped according to potential difficulty of tube insertion. In a patient with an anterior glottis or target orifice (the vocal cords and opening positioned high in the patient""s neck and to the front of the neck), placing the insertion end of the endotracheal tube through the opening can be extremely difficult, and can lead to serious injury and even death from lack of oxygen. Although careful evaluation by the anesthesiologist or healthcare practitioner may suggest difficulty, the condition is usually undetectable until the orifice and vocal cords are visualized with a laryngoscope and blade apparatus. When this occurs, the practitioner must remove the laryngoscope, and the insert a metal or plastic stylette (semi-rigid wire) into the lumen of the endotracheal tube, bend the tube and stylette into an appropriate configuration to aid in placing the insertion tip in its proper location and to act as a placement guide. A small bend, resembling the shape of a hockey stick, is made in the stylette and the end of the endotracheal tube, while the main body of the tube remains unchanged. Once this is accomplished, another attempt is made by the practitioner to visualize the vocal cords and inlet. The bent shape of the insertion tip improves the chances of passing the tip through the tracheal orifice. An example of early endotracheal tube including a stylette for curvature is described in U.S. Pat. No. 2,458,305 to Sanders.
Although this method of using a stylette to bend the insertion end of the endotracheal is widely used, it has many shortcomings. The steps of bending the tube in the correct configuration, subsequent visualizing the path of insertion, and then removing the stylette from the lumen of the endotracheal tube wastes valuable time in completing the intubation procedure. Time is of the utmost importance in an unconscious patient who is not breathing, particularly where the patient may have a full stomach with an increased chance for aspiration of foreign substance.
Also, the use of a stylette is usually employed after an initial attempt has been made with the laryngoscope in place. Further, because of there intended use stylettes must be semi-rigid, capable of being easily bent and, once bent, and shape retaining. This inherent characteristic places a patient at risk of an injury from the stylette to the airway with potential for bleeding in the airway as well. In the past, puncture of soft tissue and vocal cord damage has been attributed to the use of stylettes.
None of the prior devices have succeeded in the elimination of the use of a stylette to properly configure an endotracheal tube and successfully intubate a patient.
Many devices have been designed to assist in the placement of the tracheal tube in the target orifice. For example, laryngoscopes have been developed to aid in insertion. However, these devices do not provide any mechanism for controlling the curvature of the insertion end of the endotracheal tube itself.
U.S. Pat. No. 4,589,410 to Miller, U.S. Pat. No. 4,150,676 to Jackson and U.S. Pat. No. 4,685,457 to Donenfeld each show an endotracheal tube with at least one pull cord in the wall along a portion of the length of the tube. Applying tension on the cord causes the tube at a position proximal to the balloon to curl, apparently due to the compressibility of the material of construction. However, the tip of the tube does not bend, the bending being distributed along the whole length of the pull cord. These devices do not employ a hinge or spring-type mechanism or altered tube wall, nor do they use a locking device. As a result, these prior devices do not allow selected movement at the tip of the tube. In these prior devices, the body of the tube is moved by a pulley mechanism which bends a considerable portion of the tube, thus creating problems due movement of the tube within the mouth.
Other devices employing tube bending mechanism include U.S. Pat. No. 5,255,668 to Umeda is directed to a bendable endoscope used for broncoscopy which includes a bendable distal portion spaced between two coils in the wall of the tube, the bendable portion is caused to bend by pulling on a wire in the wall of the tube. U.S. Pat. No. 4,911,148 to Sosnowski et al. is directed to small diameter (diameter of 0.15 mm or less) endoscopes which have a series of radial notches spaced along the length of the tube and a pull wire through the notched wall. Pulling on the wire causes the tube to bend along the portion containing the notches, which in turn causes the tip to deflect. U.S. Pat. No. 5,304,131 to Paskar shows an arterial or venous catheter with an area of weakness along one side of the catheter. The weakness is the result of gaps cut through the wall of the catheter. Bending of the weakened portion is provided by a wire running through the wall on the side of the gaps. To aid in returning the weakened portion to its original straight orientation that portion may be surrounded by a spring and, to seal the weakened portion, a jacket can cover the spring and the weakened portion.
U.S. Pat. No. 4,353,358 to Emerson is directed to a flexible sigmoidoscope which has notches and a pull wire similar to Sosnowski et al. Other flexible tipped endoscopes and catheters with hinged portions and a pull wire are also shown in U.S. Pat. No. 5,772,578 to Heimberger, et al. and U.S. Pat. No. 5,448,989 to Heckele. U.S. Pat. No. 5,306,245 to Heaven shows a bendable tubular device which includes a cutaway wall opposite a flexible stainless steel hinge with a pull wire in the tube wall opposite to the hinge. At least the cut-out portion is covered by an outer plastic material. This plastic cover may also cover the pull wire, as well as the full length of the tube. A balloon may be added distal to the bendable portion. These devices do not include an occlusion balloon such as is required on an endotracheal tube. While Heaven includes a balloon, it is distal to the bendable portion and used for cholangiographic purposes and is not intended to seal a trachea.
None of these devices in the preceding two paragraphs are intended to operate in the manner of an endotracheal tube. They do not incorporate features of the invention, such that a portion of the tube near the insertion tip articulates, while the main portion of the tube remains in its original preset shape.
While there have been various changes, improvements and developments in endotracheal tubes, there still remains a need for a device that can bend only at the tip and has a mechanism to temporarily lock the position in place. Such an endotracheal tube would facilitate one-handed manipulation of the tube while the other hand is free to manipulate other devices, such as a laryngoscope. Also, this should be accomplished without having to compromise the lumen of the tube.
The endotracheal tube of the present invention has a distal end configured to be inserted into a human trachea that can be manipulated, without the use of a stylette or other guiding device, while the tip of the tube is approaching the glottis. The main tube body remains in its original configuration, while allowing the distal end to be independently curved or bent and maintained in a desired position during placement of the endotracheal tube. The lumen of the endotracheal tube remains unoccluded during the curving of the distal tip so as not to block the patient""s airways. Creating the desired distal tip curvature is accomplished by the use of various designs, all contemplated as within the scope of the invention, in combination with one or more mechanisms for manipulating the distal end of the tube. In accordance with one specific, exemplary embodiment of the invention, these include:
1) locating a spring between distal tip and main tube body;
2) using ultrasound, heat, solvent treatment or like methods, to modify the molecular structure or composition of the polymer forming the portion of the tube to be bent so as to increase flexibility of that portion;
3) using of a polymer baffle between the distal tip and main tube body;
4) surrounding the portion to be bent by a polymer spring; or
5) providing a thin, notched or cutout area between distal tip and main body tube with or without the support spring.
All of the above mechanisms may be applied to the outside of the endotracheal tube, incorporated in the wall of the tube, or inserted within the lumen of the tube. The endotracheal tube of the present invention also contemplates a control mechanism for causing movement of the tip and temporary locking of the bend which is imposed on the distal end tube. This can be accomplished by the use of a friction lock mechanism, a single axis lock, a sliding trigger with catch, a detent system, or a similar locking device which cooperates with a pull wire. This locked position permits the practitioner to have at least one hand free to manipulate other devices. In its preferred operation, one hand holds the endotracheal tube while the laryngoscope is operated with the other hand. After the curved end of the tube is inserted in its desired position, the trigger mechanism can be easily released and the tube allowed to assume its original configuration. An endotracheal tube incorporating features of the invention preferably does not have an occluded tube lumen, allows the practitioner to have superior tip control, and allows rapid achievement of airway control.